Event ID 1006: RPC Client Access Failed - Complete Fix Guide

# Get current Outlook Anywhere settings
Get-OutlookAnywhere | Format-List *

# Reconfigure Outlook Anywhere with correct settings
Get-OutlookAnywhere | Set-OutlookAnywhere -ExternalHostname "mail.domain.com" -InternalHostname "mail.domain.com" -ExternalClientAuthenticationMethod Ntlm -InternalClientAuthenticationMethod Ntlm -ExternalClientsRequireSsl $true -InternalClientsRequireSsl $true -SSLOffloading $false

# If using load balancer with SSL offloading:
# Set-OutlookAnywhere -SSLOffloading $true-SSLOffloading $true

# Set IIS authentication methods
Get-OutlookAnywhere | Set-OutlookAnywhere -IISAuthenticationMethods Ntlm, Basic, Negotiate

# Enable Outlook Anywhere if disabled
Get-OutlookAnywhere | Set-OutlookAnywhere -Enabled $true

# Restart IIS to apply changes
iisreset /noforce

# Verify configuration
Get-OutlookAnywhere | Format-List ExternalHostname, ExternalClientAuthenticationMethod,
    SSLOffloading, Enabled

# Check if MAPI over HTTP is enabled at org level
Get-OrganizationConfig | Format-List MapiHttpEnabled

# Enable MAPI over HTTP organization-wide
Set-OrganizationConfig -MapiHttpEnabled $true

# Configure MAPI virtual directory URLs
Get-MapiVirtualDirectory | Set-MapiVirtualDirectory -InternalUrl "https://mail.domain.com/mapi" -ExternalUrl "https://mail.domain.com/mapi"

# Set authentication methods
Get-MapiVirtualDirectory | Set-MapiVirtualDirectory -IISAuthenticationMethods Ntlm, OAuth, Negotiate

# Enable for specific mailboxes (if testing)
Set-CASMailbox -Identity user@domain.com -MapiHttpEnabled $true

# Force client to use MAPI/HTTP (requires Outlook 2013 SP1+)
# Registry on client: HKCUSoftwareMicrosoftExchange
# DWORD: MapiHttpDisabled = 0

# Restart IIS
iisreset /noforce

# Test MAPI connectivity
Test-MAPIConnectivity -Identity user@domain.com | Format-List

# Check RPC Proxy registry settings
Get-ItemProperty "HKLM:SOFTWAREMicrosoftRpcRpcProxy" -ErrorAction SilentlyContinue

# Verify RPC proxy is enabled in IIS
$rpcPath = "IIS:SitesDefault Web Site
pc"
if (Test-Path $rpcPath) {
    Get-WebConfigurationProperty -PSPath $rpcPath -Filter "system.webServer/security/authentication/anonymousAuthentication" -Name enabled
    Get-WebConfigurationProperty -PSPath $rpcPath -Filter "system.webServer/security/authentication/windowsAuthentication" -Name enabled
} else {
    Write-Host "RPC virtual directory not found!" -ForegroundColor Red
}

# Reset RPC virtual directory (recreate if corrupted)
# First, remove existing
Remove-WebApplication -Site "Default Web Site" -Name "rpc" -ErrorAction SilentlyContinue

# Recreate using Exchange setup
# Run from Exchange installation media:
# Setup.exe /PrepareSchema /IAcceptExchangeServerLicenseTerms

# Or manually create the RPC vdir
New-WebApplication -Site "Default Web Site" -Name "rpc" -PhysicalPath "C:Program FilesMicrosoftExchange ServerV15FrontEndHttpProxy
pc"

# Configure authentication
Set-WebConfigurationProperty -PSPath "IIS:SitesDefault Web Site
pc" -Filter "system.webServer/security/authentication/anonymousAuthentication" -Name enabled -Value $false
Set-WebConfigurationProperty -PSPath "IIS:SitesDefault Web Site
pc" -Filter "system.webServer/security/authentication/windowsAuthentication" -Name enabled -Value $true

# Restart IIS
iisreset /noforce

# Check RPC Client Access service dependencies
$service = Get-Service MSExchangeRPC
$deps = $service.DependentServices + $service.ServicesDependedOn
$deps | Select-Object Name, Status, StartType | Format-Table -AutoSize

# Verify AD connectivity
$dc = [System.DirectoryServices.ActiveDirectory.Domain]::GetCurrentDomain().FindDomainController()
Write-Host "Connected to DC: $($dc.Name)"

# Test LDAP connectivity
Test-NetConnection -ComputerName $dc.Name -Port 389 -InformationLevel Detailed

# Check if Exchange can query AD
Get-ADServerSettings | Format-List ViewEntireForest, RecipientViewRoot

# Verify service account permissions
$exchangeServers = Get-ADGroupMember "Exchange Servers"
$exchangeServers | Format-Table Name, objectClass

# Reset service if stuck
Stop-Service MSExchangeRPC -Force
Start-Sleep -Seconds 5
Start-Service MSExchangeRPC

# If service won't start, check for stuck processes
Get-Process | Where-Object {$_.Name -like "*exchange*"} | Stop-Process -Force
Start-Service MSExchangeRPC

# Force Outlook to re-discover settings (run on client)
# Delete Autodiscover cache
Remove-Item "$env:LOCALAPPDATAMicrosoftOutlook*.xml" -Force -ErrorAction SilentlyContinue

# Clear credential cache
cmdkey /list | ForEach-Object {
    if ($_ -match "Target: (.+)") {
        $target = $Matches[1].Trim()
        if ($target -match "exchange|outlook|office") {
            cmdkey /delete:$target
        }
    }
}

# Reset Outlook profile (nuclear option)
# Control Panel > Mail > Show Profiles > Remove

# Create new Outlook profile via registry (for deployment)
$profileName = "NewProfile"
New-Item "HKCU:\Software\Microsoft\Office\16.0\Outlook\Profiles\$profileName"0\Outlook\Profiles\$profileName" -Force

# Disable Cached Exchange Mode temporarily (for testing)
# In Outlook: File > Account Settings > Change > uncheck "Use Cached Exchange Mode"

# Check Outlook connectivity logging
# Enable: File > Options > Advanced > Enable troubleshooting logging
# Logs at: %TEMP%Outlook Logging

# Force specific protocol (MAPI/HTTP or RPC/HTTP)
# HKCUSoftwareMicrosoftExchange
# DWORD: MapiHttpDisabled = 0 (for MAPI/HTTP) or 1 (for RPC/HTTP)1 (for RPC/HTTP)